This invention relates to a crimping apparatus for crimping a metal terminal to an electric wire and also to a metal terminal crimped to an electric wire by the crimping apparatus.
FIG. 6 shows one known conventional crimping apparatus. A metal terminal 107 includes a pair of crimping piece portions 108 and 109 extending upwardly respectively from opposite side edges of a base plate portion on which an electric wire 106 is adapted to be placed. One crimping piece portion 109 is longer than the other crimping piece portion 108. A crimper 101 of the crimping apparatus for crimping the metal terminal 107 to the electric wire 106 has a notched groove 102, and introduction guide portions 103, pressing portions 104 and a curved portion 105 are formed on an inner surface of the notched groove 102 (see, for example, JP-A-7-73950).
The pair of crimping piece portions 108 and 109 are press-fastened (press-deformed) by the crimper 101 of the above construction in such a manner that the one crimping piece portion 109 overlaps the other crimping piece portion 108, and further a distal end portion of the crimping piece portion 108 is curved and deformed in a direction opposite to the press-fastening direction, and is engaged with an inner surface of the crimping piece portion 109.
FIG. 7 shows another known conventional crimping apparatus. Two arch-shaped portions arranged symmetrically with respect to a plane in adjoining relation are formed on an inner surface 112 of a crimper 111 for press-fastening a pair of crimping piece portions 117 of a metal terminal 116 to an electric wire 115. Each arch-shaped portion is formed by an arc-shaped portion 113 with a radius R1 and an arc-shaped portion 114 with a radius R2, and centers of circles on which the arc-shaped portions 113 and 114 are disposed, respectively, lie on an imaginary straight line A passing through an apex of the arch-shaped portion (see, for example, JP-UM-A-61-48681).
In each of JP-A-7-73950 and JP-UM-A-61-48681, an attempt has been made to improve the shape of the crimper so as to enhance electrical and mechanical performances of the crimped portion. However, when trying to change the shape of a crimper, the crimper tends to be formed into a complicated shape as in the crimper 101 of JP-A-7-73950 and the crimper 111 of JP-UM-A-61-48681, and there are fears that the time and labor required for producing the crimper may increase and that it may be difficult to maintain its processing precision.
Furthermore, in JP-A-7-73950, the press-fastened crimping piece portions 108 and 109 assume a complicated shape, and there is a fear that an increased load is applied to the crimping piece portions 108 and 109 during the press-fastening operation, and there is a fear that problems such as insufficient strength of the press-fastened crimping piece portions 108 and 109, the separation of a plating layer, etc., may be encountered.
In connection with the design of a connector and a metal terminal, many limitations are imposed on a crimper which is a main factor in the definition of the shape of the crimped metal terminal. For example, in the case where the metal terminal is crimped to a very thin electric wire with a core wire having a cross-sectional area of not more than 0.13 mm2, a width of a groove in the crimper is usually limited to not more than 1.0 mm, and this groove width can not be freely increased, and the conventional techniques for improving the shape of the crimper can not always deal with this situation.